Data generated by sensors and devices is used by various applications. Examples of data generated by sensors include sensing data such as temperature, humidity, water level, wind speed, electric power consumption, position information, and so forth. On the other hand, examples of data generated by devices include sales data from point-of-sale (POS) terminals and vending machines, various types of correlation data such as weather and so forth at the point that a product was sold, data on the operating state of a device, stock data on products, and so forth. Data generated by sensors and devices are great both in amount and variety, and further the amount of data increases over time. Data is transmitted over a network to a data center or the like, for example, to accumulate the great amount of data generated periodically by sensors and devices. Data accumulated in the data center is transferred via network to locations corresponding to various applications which use this data, as these applications are executed.
Now, there known is a technique in which stream data is accumulated in data accumulating devices fixedly assigned by multiple data accumulating devices so as to be used. There is also known a technique in which the speed of processing for generated compressed data to be further recompressed is increased, in order to reduce the amount of communication at the time of generating information from multiple devices. There is further known a technique in which files, which have to be saved for a predetermined amount of time even though the frequency of usage is small, from the perspective of compliance and so forth, are relocated from an expensive hard disk drive to an inexpensive hard disk drive when usage frequency becomes low. Moreover, there is known a technique to extract difference of log files.
The aforementioned related art is described in, for example, Japanese Laid-open Patent Publication No. 2008-294774, International Publication Pamphlet No. 2008/105406, Japanese Laid-open Patent Publication No. 2008-071035, and Japanese Laid-open Patent Publication No. 2010-257330.